Frederica Sagor Maas went to Hollywood in her early 20s determined to be a writer.

She contributed to the films of cinema greats such as Louise Brooks and Greta Garbo, but did not find fame herself until the publication of her memoir The Shocking Miss Pilgrim: a writer in early Hollywood. She once advised me "Don't live past 90. It gets boring"; she died at the astonishing age of 111.

Frederica Sagor was born in 1900 to Russian émigré parents in New York. She read widely, and a radical teacher taught her more about the treatment of the Indian, the hysteria of the Salem witch trials and the truth about slavery than was customary: "Accept nothing" she would say. "Examine, challenge, think it out for yourself."

"It was this skill, more than any other, that helped me to navigate the rocks and rapids of my future life in Hollywood" she later said. She enrolled at Columbia University but its journalism course disappointed her. She joined the New York Globe as a copygirl then spotted an ad for a job as assistant to a story editor at Universal Pictures. The editor John Brownell offered her $100 a week, more than her father earned as a tailor.

She saw all the new movies, making notes and studying them. She fell in love with her boss, and he with her, and to save his marriage he left the company. His replacement was an alcoholic; Universal fired him, doubled Sagor's salary and put her in charge. She accepted on condition that at the end of the year Universal would send her to the West Coast to join the writing staff at Universal City. Before that she came across William Wyler, who wanted to work in the story department. She thought he would do better in the cutting room; he took her advice, and eventually became one of the greatest film-makers in Hollywood.

Sagor was responsible for the Clara Bow hit The Plastic Age, based on a novel by a Brown University professor which exposed the drinking and wild socialising in modern college life. She bought the book but the head of Universal, Carl Laemmle, had just been appointed head of the Clean Picture Campaign. He regarded it as a "dirty book" and refused to film it. Sagor sold the property for a $10,000 profit and Laemmle pocketed the cheque without a word.

Universal having reneged on its promise to send her to the West Coast, Sagor resigned and went under her own steam. She contacted the company to whom she had sold The Plastic Age and was hired by BP Schulberg to write the scenario. She next found work at MGM with the B-picture producer Harry Rapf, who gave her the script for Dance Madness, to "fix"; she did the rewrite in five days and she got full credit and an assignment to the Norma Shearer unit.

The big executives' secretaries politicised Frederica. "The studio waste, dirty politics, devious schemes, head chopping, ruthless ambition, greed, power out of control, debauchery so prevalent in this girlie business – in our young political eyes these were all manifest consequences of unleashed capitalism."

She joined a group from MGM meeting off the train a new starlet, Lucille LeSueur, later Joan Crawford. A week later, LeSueur appeared in her office: 'You dress like a lady, I like that. I want to be dressed smart." They went shopping. "She had class," said Sagor, "even if it showed only in her wardrobe."

In 1925 she wrote His Secretary for Norma Shearer. Carey Wilson, head of the scenario department, removed her name from the script and attached his own. "Don't worry" he said. "You'll get screen credit in the end." She didn't.

Sagor worked on a preliminary draft for Flesh and the Devil, Garbo's third vehicle for MGM and a phenomenal hit. Then on The Waning Sex, she worked with an English writer, F Hugh Herbert, who, after a long, difficult writing session asked her to marry him. She refused: "And I am sure he never forgave me." When she criticised his work to Rapf, her boss told her that they were going to shoot Herbert's story, not hers.

Eager to free herself from Rapf, she asked to join producer Hunt Stromberg's unit. Instead, Rapf, regarding her as a troublemaker, had her fired. She found work at the poverty-row company Tiffany, where in 1926 she worked on the frivolous comedy That Model From Paris. The thought of a career writing froth made her anxious to quit, but in 1927 she married Ernest Maas, a producer at Fox. "In all the time I had been in Hollywood, I had encountered no one so knowledgeable, discerning, and voluble with such a span of interests so close to my own." They had to endure their script ideas being rejected by other companies, only to be produced under the camouflage of misleading titles. They dared not sue, knowing that an industry blacklist could end their careers. But when The Way of all Flesh won for Emil Jannings a first Academy Award for acting, they felt heartsick.

They lost thousands in the Wall Street crash of 1929, and nearly lost their lives in the Newport Beach earthquake of 1933. Moving to New York, they watched as the homeless across the street built shelters from packing cases. They offered help, but the commune was burned by city workers.

She became an agent, but hated the work. During the Great Depression, she considered suicide. In 1941, the couple produced their last major screenplay, Miss Pilgrim's Progress, about the revolution of the "typewriters" – the women rather than the machines – who transformed the solidly male clerical profession and emancipated females from domestic drudgery. She said it was the story she was proudest to have written.

Four studios pursued the property, and Fox paid $15,000, but producer Darryl Zanuck had it rewritten as a musical for Betty Grable. It appeared in 1947 as The Shocking Miss Pilgrim, and, although Sagor wrote that it was a "howling box office success", it was the only out and out failure for the No 1 female star of the 40s.

The Maases found themselves doctoring other people's scripts but failing to sell their own. During the McCarthy era they were pressured to name names during three FBI interrogations, though not members of the Communist Party. Once again, suicide seemed the only option. They chose the spot – an isolated hilltop – but couldn't go through with it. Their Hollywood days over, Frederica worked in an insurance office. In 1998 her memoir appeared; her eyesight deteriorated badly, but she continued to be able to touch-type.

Frederica Sagor, screenwriter: born New York 6 July 1900; married 1927 Ernest Maas (died 1986); died La Mesa, California 5 January 2012.